Methods for forming wrap around contact

ABSTRACT

Some embodiments of the present disclosure relate to a contact formed to a source or drain region of a “finned” field-effect transistor (FinFET). An epitaxial material is formed over the source or drain region, which includes a diamond-shaped cross-section with top and bottom surfaces. A capping layer is formed over the top and bottom surfaces. The source or drain region is subjected to a first etch to remove the capping layer surrounding the top surfaces of the diamond-shaped cross-section. A protective layer is formed within the top surfaces. A second etch of the capping layer is performed to remove the capping layer surrounding the bottom surfaces of the diamond-shaped cross-section, while using the protective layer to prevent etching of the top surfaces by the second etch. A contact is formed to the source or drain region, which surrounds the source or drain region on the top and bottom surfaces.

BACKGROUND

The following disclosure relates to semiconductor manufacturing methods.In particular, the following disclosure relates to a contact formed to asemiconductor device and a method of forming the contact.

Nonplanar semiconducting devices such as “finned” field-effecttransistors (FinFETs) formed on a silicon substrate include a siliconfin that forms the source and drain regions of the finFET. The sourceand drain regions are separated by a channel region, and a gate “wraps”around the upper surface and sidewalls of the channel region. The finnedstructure of the channel region increases the effective gate width ofthe FinFET over a planar FET, which allows for increased gate control ofthe channel region.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1C illustrate some embodiments of a “finned” field-effecttransistor (FinFET) with a wrap-around source or drain contact.

FIG. 2 illustrate some embodiments of a method to form a wrap-aroundcontact to a source or drain region of a FinFET.

FIGS. 3A-3B, 4A-4B, 5A-5B, 6A-6B, 7A-7B, and 8A-8B illustrate a seriesof cross-sectional views that collectively depict some embodiments offorming a wrap-around contact to a source or drain region of a FinFET.

FIG. 9 illustrate some embodiments of a method of capping layer removalfor wrap-around contact formation to a source or drain region of aFinFET.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the subject matter.Specific examples of components and arrangements are described below tosimplify the present disclosure. These are, of course, merely examplesand are not intended to be limiting. For example, the formation of afirst feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “over,” “on,” “beneath,”“below,” “lower,” “above,” “upper” and the like, may be used herein forease of description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

Wrap-around contact formation to the source or drain of a “finned”field-effect transistor (FinFET) allows for increased contact area tolower contact resistance and increase performance of the FinFET over aplanar FET. Some FinFETs utilize a layer of epitaxial material toproduce strain within the channel region to increase carrier mobilityand hence further increase FinFET performance. The epitaxial materialhas a diamond-shaped cross-section with top and bottom surfaces that arecovered with a capping layer, which must be removed prior to contactformation.

Some conventional methods of capping layer removal around thediamond-shaped epitaxial material comprise a dry etch to remove thecapping layer material from the top surfaces of the diamond-shape toexpose the epitaxial material on the top surfaces. However, the bottomsurfaces are not exposed to the dry etchant. As a result, the dry etchdoes not remove the capping layer material on bottom surfaces. Removalof the capping layer material from bottom the surfaces can increasecontact area for the wrap-around contact. Therefore, some conventionalmethods also use a wet etch to remove the capping layer material frombottom the surfaces.

In some instances, the dry etch includes an O₂ plasma that causesoxidation of the epitaxial material. The oxidized epitaxial materialreacts with the wet etchant during the wet etch step, which results insignificant loss of the epitaxial material from the source or drainregion, and reduces strain within the channel region and consequentlydecreases carrier mobility. Loss of the epitaxial material alsodecreases contact area of the wrap-around contact. These effects candegrade FinFET performance.

Accordingly, some embodiments of the present disclosure relate to awrap-around contact formed to a source or drain region of a FinFET. Anepitaxial material is formed over the source or drain region, whichincludes a diamond-shaped cross-section with top and bottom surfaces. Acapping layer is formed over the top and bottom surfaces. The source ordrain region is then subjected to a first etch to remove the cappinglayer surrounding the top surfaces of the diamond-shaped cross-section.A protective layer is formed within the top surfaces. A second etch ofthe capping layer is performed to remove the capping layer surroundingthe bottom surfaces of the diamond-shaped cross-section, while using theprotective layer to prevent etching of the top surfaces by the secondetch. A wrap-around contact is formed to the source or drain region,which surrounds the source or drain region on the top and bottomsurfaces of the diamond-shaped cross-section.

The FinFET and methods of wrap-around contact formation disclosed hereinprevent the loss of epitaxial material from the source or drain regionsthat are observed in some conventional methods. The resultantwrap-around contact does not experience the loss of channel regionstrain or reduced contact area due to epitaxial material loss. Thewrap-around contact also contacts the top and bottom surfaces of theepitaxial material, which increases the contact area over someconventional methods where the capping layer on the bottom surfaces isnot fully removed.

FIG. 1A illustrates some embodiments of a FinFET 100. The FinFET 100 isformed on a semiconductor substrate 102, and comprises twosemiconducting fins 104 arranged in parallel (i.e., along the y-axis)and extending vertically (i.e., along the z-axis) from a surface 106 ofthe semiconductor substrate 102. For the embodiments of the FinFET 100,the semiconducting fins 104 are isolated from one-another by anisolation layer 108 formed over the semiconductor substrate 102. Thesemiconducting fins 104 comprise source and drain regions 110, 112,which are separated from one another by a channel region 114. A gate 118overlays the channel region 114 of each semiconducting fin 104.

The FinFET 100 includes an epitaxial material 120 formed over the sourceand drain regions 110, 112 of each semiconducting fin 104. The epitaxialmaterial 120 comprises a diamond-shape along cross-section AA′ of theFinFET 100 width (i.e., the face of the FinFET 100 along the xz-plane).A wrap-around contact 122 is formed to each source and drain region 110,112, and surrounds the epitaxial material 120 formed over each source ordrain region 110, 112 on top and bottom surfaces 124, 126 of thediamond-shaped cross-section. A connecting structure 134 (e.g., contact,via, local interconnect, etc.) can then be used to couple the source ordrain region 110, 112 to an external voltage source.

FIG. 1B illustrates a view of the FinFET 100 along cross-section AA′,which shows the diamond-shaped cross-section of the epitaxial material120. FIG. 1B includes several features that result from the method offormation of the wrap-around contact 122. Capping material 128 residesnear a bottom portion of the sidewalls of each semiconducting fin 104 atan interface to an upper surface 130 of the isolation layer 108. Contactresidue 132 (i.e., material of the wrap-around contact 122) resides onthe upper surface 130 of the isolation layer 108 between the fins 104.

FIG. 1C illustrates a view of the FinFET 100 along cross-section BB′ ofthe FinFET 100 length (i.e., bisecting a fin 104 of FinFET 100 along theyz-plane of FIG. 1A). The source, drain, and channel regions 110, 112,114 are also illustrated. In some embodiments, the epitaxial material120 formed on each fin 104 is configured to exert strain on the channelregion 114 due to a lattice constant mismatch between the epitaxialmaterial 120 and the fin 104. This strain increases carrier mobilitywithin the channel region 114.

FIG. 2 illustrates some embodiments of a method 200 to form awrap-around contact to a source or drain region of a FinFET.

At 202 a semiconducting fin is formed that extends vertically from asurface of a substrate. The semiconducting fin comprises source anddrain regions which are separated from one another by a channel region.An epitaxial material is formed over the source or drain regions, andincludes a diamond-shaped cross-section. A capping layer is formed thatsurrounds the diamond-shaped cross-section on its top and bottomsurfaces. The capping layer is configured to protect the epitaxialmaterial from various layer deposition and removal steps the FinFET.

At 204 a gate is formed that overlays an upper surface and sidewalls ofthe channel region of the semiconducting fin. In some embodiments, thegate comprises polysilicon. In some embodiments, the gate comprises areplacement metal gate (RMG). It will be appreciated that in someembodiments the source or drain regions formed in 202 can be formedafter the gate is formed (e.g., a self-aligned process).

At 206 a first etch is performed to remove a first portion of thecapping layer surrounding the top surfaces of the diamond-shapedcross-section of the epitaxial material. In some embodiments, the firstetch utilizes a dry etch, wet etch, or combination thereof.

At 208 a protective layer is formed within the top surfaces of thediamond-shaped cross-section. The protective layer is configured toprevent etching of the top surfaces in subsequent etch steps intended toremove the capping layer from the bottom surfaces of the diamond-shapedcross-section.

At 210 a second etch is performed to remove a second portion of thecapping layer surrounding the bottom surfaces of the diamond-shapedcross-section, while using the protective layer to prevent etching ofthe top surfaces of the diamond-shaped cross-section by the second etch.

At 212 a wrap-around contact is formed to the source or drain region.The wrap-around contact surrounds the source or drain region on the topand bottom surfaces of the diamond-shaped cross-section, and contactsthe epitaxial material on the top and bottom surfaces. By contacting theepitaxial material on the top and bottom surfaces, the wrap-aroundcontact has less contact resistance than if it were formed on the topsurfaces only, or if the capping layer was not fully-removed from thebottom surfaces by the second etch, thus preventing the wrap-aroundcontact from contacting the bottom surfaces.

FIGS. 3A-3B, 4A-4B, 5A-5B, 6A-6B, 7A-7B, and 8A-8B illustrate a seriesof cross-sectional views that collectively depict some embodiments offorming a wrap-around source or drain contact to a source or drainregion of a FinFET.

FIG. 3A illustrates the FinFET 100 along cross-section AA′ prior towrap-around contact formation. An oxide material 304 is disposed overthe epitaxial material 120 on each semiconducting fin 104. The oxidematerial 304 is also formed on an upper surface of the isolation layer108 between a pair of semiconducting fins 104. The capping material 128is disposed over the oxide material 304. A dielectric material 302 isthen formed over the substrate 102 and around the pair of semiconductingfins 104. In some embodiments, the capping material comprises siliconnitride (SiN).

FIG. 3B illustrates the FinFET 100 along cross-section BB′ (i.e.,bisecting a fin 104 of FinFET 100 along the yz-plane of FIG. 1A) priorto wrap-around contact formation. The oxide material 304 and cappingmaterial 128 are formed on both the top and bottom surfaces 306, 308 ofthe epitaxial material 120. A mask layer 310 forms a pattern for asubsequent etch of the dielectric material 302. In some embodiments, themask layer 310 comprises photoresist. In some embodiments, the epitaxialmaterial 120 comprises germanium (Ge) or silicon-germanium (SiGe)configured to exert strain on the channel region 114 due to a latticeconstant mismatch between the epitaxial material 120 and thesemiconducting fin 104 comprising silicon (Si).

FIGS. 4A-4B illustrate the FinFET 100 along cross-sections AA′ and BB′after removal of the dielectric material 302, and a first etch to removecapping material 128 from the top surface 306 of the epitaxial material120. Removal of the dielectric material 302 exposes the capping material128 on the top and bottom surfaces 306, 308 of the epitaxial material120. In some embodiments, removal of the dielectric material 302 isachieved by an etch. For the embodiments of FIGS. 4A-4B, the first etchincludes a plasma etch with comprise hexafluoro-1, 3-butadiene (C₄F₆)etch and argon (Ar). The plasma etch also results in damage 402 to theepitaxial material 120 near the top surface 306. After removal of thedielectric material 302, the first etch is performed to remove thecapping material 128 from the top surfaces 306 of the epitaxial material120 to expose the oxide material 304 on the top surfaces 306 of theepitaxial material 120. In some embodiments, the first etch comprises adry etch with fluoride (CH₃F) and hydrogen (H₂).

Some conventional approaches of dielectric material 302 removal utilizean O₂ ash plasma to remove a mask layer 310 of photoresist after thefirst etch. The O₂ ash plasma treatment can cause oxidation of theepitaxial material 120, which decreases etch selectivity between theepitaxial material 120 and capping material 128. To combat the effectsof oxidation of the epitaxial material 120, the photoresist removal ofthe embodiments of FIGS. 4A-4B uses a diazene (N₂H₂) ash process.

FIGS. 5A-5B illustrate the FinFET 100 along cross-sections AA′ and BB′after formation of a protective material 502 within the top surfaces 306of the epitaxial material 120. The protective material 502 is configuredto prevent etching of the top surfaces 306 in subsequent etch steps toprevent loss of the epitaxial material 120. The protective material 502is also formed between the pair of fins 104 over a surface of theisolation layer 108. The protective material 502 is configured toprovide for better etch selectivity between itself and the remainingcapping material 128 than between the epitaxial material 120 and thecapping material 128. This increased selectivity helps prevent loss ofthe protective material 502 in a subsequent etch step to remove thecapping material 128 from the bottom surfaces 308 of the epitaxialmaterial 120.

In some embodiments, formation of the protective material 502 comprisesperforming a carbon (C) implant 504 of the top surfaces 306. In someembodiments, the carbon implant is performed with little to no implantangle or rotation (i.e., 0° tilt and 0° rotation). In some embodiments,the carbon implant is performed at a relatively low energy (e.g.,between about 0.5 keV and about 10 keV). In some embodiments, the carbonimplant is performed with a dosage in a range of about 1e13 cm⁻² toabout 1e16 cm⁻². In some embodiments, the carbon implant is performedwith a depth range of about 1 nm to about 100 nm. In some embodiments,the carbon implant is performed with a peak carbon concentration ofabout 0.1% to about 5%. In some embodiments, the protective layercomprises silicon-carbon-phosphorus (SiCP), silicon-carbon-germanium(SiGeC), or germanium-carbon (GeC).

The C implant 504 also interacts with the oxide material 304 on the topsurfaces 306 of the epitaxial material 120 and on sides of the gate 118to form an implanted oxide 506.

FIGS. 6A-6B illustrate the FinFET 100 along cross-sections AA′ and BB′,wherein the oxide material 304 (or implanted oxide 506 byproduct of theC implant 504 of FIGS. 5A-5B) has been removed from the top surfaces 306of the epitaxial material 120. A second etch is then performed to removethe capping material 128 from the bottom surfaces 308 of the epitaxialmaterial 120. The second etch utilizes an etchant with a selectivitybetween the protective material 502 and capping material 128 such thatthe capping material 128 is etched at a higher rate than the protectivematerial 502. As a result, the epitaxial material 120 is leftsubstantially intact.

The protective material 502 therefore protects the epitaxial material120 from the second etch. As a result, the capping material 128 isremoved from the bottom surfaces 308, while leaving the diamond-shapedepitaxial material 120 substantially intact. After the second etch, theremaining oxide material 304 has been removed from the bottom surfaces308 to expose the epitaxial material 120 on the bottom surfaces 308.While some of the capping material 128 remains at the base of one ormore fins 104, the capping material 128 is removed from the top andbottom surfaces 306, 308 of the epitaxial material 120 to allow forincreased contact area to the epitaxial material 120.

In some embodiments, the oxide material 304 (or implanted oxide 506) isremoved with dilute hydrofluoric acid (DHF). In some embodiments, thesecond etch comprises a wet etch phosphoric acid (H₃PO₄).

FIGS. 7A-7B illustrate the FinFET 100 along cross-sections AA′ and BB′,wherein a conducting material 702 has been deposited over the surface ofthe substrate 102, including the epitaxial material 120 and fins 104.The conducting material 702 surrounds the diamond-shaped cross-sectionof epitaxial material 120 on its top and bottom surfaces 306, 308. Insome embodiments, the conducting material 702 comprises nickel (Ni).

FIGS. 8A-8B illustrate the FinFET 100 along cross-sections AA′ and BB′,wherein a conducting material 702 has been annealed, resulting in areaction between the conducting material 702 and epitaxial material 120.Non-reacting conducting material 702 (i.e., not touching the epitaxialmaterial 120) has been subsequently removed. The remaining reactingmaterial forms wrap-around contacts 802.

In some embodiments, the conducting material 702 comprises Ni and theepitaxial material comprises germanium (Ge) or silicon-germanium (SiGe).The reaction caused by the anneal results in wrap-around contacts 802comprising nickel-germanium (NiGe) or nickel-silicon-germanium (NiSiGe),respectively.

FIG. 9 illustrates some embodiments of a method of capping layer removalfor wrap-around contact formation to a source or drain region of aFinFET.

At 902 source and drain regions of semiconducting material are formed.The source and drain regions are separated from one another by a channelregion, and have top and bottom surfaces. In some embodiments, thesource and drain regions comprise a plurality of semiconducting fins(e.g., Si fins formed by recessing a Si substrate). In some embodiments,the semiconducting fins are covered with an epitaxial material (e.g.,Ge, SiGe, etc.) configured to impart strain of the channel region due toa lattice mismatch between the epitaxial material and substratematerial. In some embodiments, the epitaxial material has the top andbottom surfaces.

At 904 a capping material (e.g., SiN) is formed that surrounds the topand bottom surfaces of the source and drain regions. The cappingmaterial comprises an etch stop layer configured to prevent etching ofthe source and drain regions while manufacturing the FinFET.

At 906 a dielectric material is formed over the capping material and isconfigured to electrically isolate the FinFET from other devices on thesubstrate.

At 908 the dielectric material is removed to expose the capping materialon the top and bottom surfaces of the source and drain regions. In someembodiments, removing the dielectric material comprises a comprisehexafluoro-1, 3-butadiene (C₄F₆) plasma etch, an argon (Ar) plasma etch,or a combination thereof.

At 910 a first etch is performed. The first etch is configured to removethe capping material from the top surfaces of the source or drain regionto expose the semiconducting material on the top surfaces. In someembodiments, the first etch comprises a dry etch with fluoride (CH₃F),hydrogen (H₂), or a combination thereof.

At 912 a second etch configured to remove the capping layer from thebottom surfaces of the source or drain region to expose thesemiconducting material on the bottom surfaces. The second etch utilizesan etchant with a selectivity between the semiconducting material andcapping material such that the capping material is etched at a higherrate than the semiconducting material. In some embodiments, the secondetch comprises a wet etch phosphoric acid (H₃PO₄), dilute hydrofluoricacid (DHF), or a combination thereof.

Therefore, some embodiments of the present disclosure relate to awrap-around contact formed to a source or drain region of a “finned”field-effect transistor (FinFET). An epitaxial material is formed overthe source or drain region, which includes a diamond-shapedcross-section with top and bottom surfaces. A capping layer is formedover the top and bottom surfaces. The source or drain region is thensubjected to a first etch to remove the capping layer surrounding thetop surfaces of the diamond-shaped cross-section. A protective layer isformed within the top surfaces. A second etch of the capping layer isperformed to remove the capping layer surrounding the bottom surfaces ofthe diamond-shaped cross-section, while using the protective layer toprevent etching of the top surfaces by the second etch. A wrap-aroundcontact is formed to the source or drain region, which surrounds thesource or drain region on the top and bottom surfaces of thediamond-shaped cross-section.

In some embodiments, the present disclosure relates to a semiconductordevice, comprising a semiconducting fin extending vertically from asurface of the substrate and comprising source and drain regions, whichare separated from one another by a channel region. A gate overlays anupper surface and sidewalls of the channel region. And, a contact isformed to the source or drain region of the semiconducting fin, whereinthe source or drain region comprises a layer of epitaxial material witha diamond-shaped cross-section, and wherein the contact surrounds thesource or drain region on top and bottom surfaces of the diamond-shapedcross-section.

In some embodiments, the present disclosure relates to a method forforming a semiconductor device. The method comprises forming a fin thatextends vertically from a surface of a substrate and comprises sourceand drain regions which are separated from one another by a channelregion, wherein the source or drain region comprises epitaxial materialwith a diamond-shaped cross-section, and wherein a capping layersurrounds the diamond-shaped cross-section on its top and bottomsurfaces. The method further comprises forming a gate overlaying anupper surface and sidewalls of the channel region. The method furthercomprises performing a first etch to remove a first portion of thecapping layer surrounding the top surfaces of the diamond-shapedcross-section. The method further comprises forming a protective layerwithin the top surfaces of the diamond-shaped cross-section, wherein theprotective layer is configured to prevent etching of the top surfaces insubsequent etch steps.

In some embodiments, the present disclosure relates to a method,comprising forming source and drain regions of semiconducting materialwhich are separated from one another by a channel region, wherein thesource or drain region has top and bottom surfaces. The method furthercomprises forming a capping material that surrounds the top and bottomsurfaces of the source or drain region, and forming a dielectricmaterial over the capping material. The method further comprisesremoving the dielectric material and expose the capping material on thetop and bottom surfaces of the source or drain region. The methodfurther comprises performing a first etch configured to remove thecapping material from the top surfaces of the source or drain region toexpose the semiconducting material on the top surfaces. The methodfurther comprises performing a second etch configured to remove thecapping layer from the bottom surfaces of the source or drain region toexpose the semiconducting material on the bottom surfaces. The secondetch utilizes an etchant with a selectivity between the semiconductingmaterial and capping material such that the capping material is etchedat a higher rate than the semiconducting material.

While methods 200 and 900 have been described as a series of acts orevents, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: forming a fin that extendsvertically from a surface of a substrate and comprises source and drainregions which are separated from one another by a channel region,wherein the source or drain region comprises epitaxial material with adiamond-shaped cross-section, and wherein a dielectric layer surroundstop and bottom surfaces of the diamond-shaped cross-section, and whereina capping layer surrounds top and bottom surfaces of the dielectriclayer and is separated from the epitaxial material by the dielectriclayer; forming a gate over an upper surface of the channel region andalong sidewalls of the channel region; performing a first etch to removea first portion of the capping layer while leaving the dielectric layersurrounding the top surfaces of the diamond-shaped cross-section; andforming a protective layer configured to prevent etching of the topsurfaces in subsequent etch steps.
 2. The method of claim 1, whereinforming the protective layer comprises implanting the top surfaces withcarbon (C) to form the protective layer within the top surfaces of thediamond-shaped cross-section.
 3. The method of claim 2, wherein theprotective layer comprises silicon-carbon-phosphorus (SiCP),silicon-carbon-germanium (SiGeC), germanium-carbon (GeC), or acombination of two or more of the following three materials: SiCP,SiGeC, and GeC.
 4. The method of claim 1, wherein the capping layercomprises silicon nitride, and wherein performing the first etchcomprises performing a dry etch with an etchant comprising fluorine,hydrogen, or a combination of fluorine and hydrogen.
 5. The method ofclaim 1, further comprising performing a second etch to remove a secondportion of the capping layer surrounding the bottom surfaces of thediamond-shaped cross-section, while using the protective layer toprevent etching of the top surfaces of the diamond-shaped cross-sectionby the second etch.
 6. The method of claim 5, wherein the capping layercomprises silicon nitride, wherein performing the second etch comprisesperforming a wet etch with an etchant comprising phosphoric acid (H₃PO₄)and dilute hydrofluoric acid (DHF).
 7. The method of claim 5, furthercomprising forming a contact to the source or drain region, wherein thecontact surrounds the source or drain region on the top and bottomsurfaces of the diamond-shaped cross-section and contacts the epitaxialmaterial on the top and bottom surfaces.
 8. The method of claim 7,wherein forming the contact comprises: depositing a conductive materialwhich surrounds the source or drain region on the top and bottomsurfaces of the diamond-shaped cross-section; and annealing thesubstrate, which causes the conductive material to react with the sourceor drain region to form the contact.
 9. The method of claim 8, whereinthe source or drain region comprises germanium (Ge) or silicon-germanium(SiGe).
 10. The method of claim 9, wherein the conductive materialcomprises nickel (Ni) and wherein the contact comprises nickel-germanium(NiGe), nickel-silicon-germanium (NiSiGe), or a combination of NiGe andNiSiGe.
 11. A method, comprising: forming source and drain regions ofsemiconductor material which are separated from one another by a channelregion, wherein the source or drain region has top and bottom surfaces,forming a capping material that surrounds the top and bottom surfaces ofthe source or drain region; forming a dielectric material over thecapping material; removing the dielectric material to expose the cappingmaterial on the top and bottom surfaces of the source or drain region;performing a first etch configured to remove the capping material fromthe top surfaces of the source or drain region to expose thesemiconductor material on the top surfaces; and performing a second etchconfigured to remove the capping material from the bottom surfaces ofthe source or drain region to expose the semiconductor material on thebottom surfaces, wherein the second etch utilizes an etchant with aselectivity between the semiconductor material and capping material suchthat the capping material is etched at a higher rate than thesemiconductor material.
 12. The method of claim 11, wherein removing thedielectric material comprises a hexafluoro-1, 3-butadiene (C₄F₆) plasmaetch, an argon (Ar) plasma etch, or a combination of a hexafluoro-1,3-butadiene (C₄F₆) plasma etch and an argon (Ar) plasma etch.
 13. Themethod of claim 11, wherein the first etch comprises a dry etch withfluorine, hydrogen, or a combination of fluorine and hydrogen.
 14. Themethod of claim 11, wherein the second etch comprises a wet etchphosphoric acid (H₃PO₄).
 15. A method, comprising: forming asemiconductor fin extending vertically from a surface of a substrate andcomprising source and drain regions in or on the semiconductor fin,where the source and drain regions have diamond-shaped cross sectionsand are separated from one another by a channel region in thesemiconductor fin; forming a capping layer that surrounds top and bottomsurfaces of the diamond-shaped cross-sections of the source and drainregions; performing a first etch to remove at least a first portion ofthe capping layer from the top surfaces of the diamond-shapedcross-section; forming a protective layer over the top surfaces of thediamond-shaped cross-section; performing a second etch to remove asecond portion of the capping layer from the bottom surfaces of thediamond-shaped cross-section, while using the protective layer to limitetching of the top surfaces of the diamond-shaped cross-section by thesecond etch; and forming a source or drain contact that conformallysurrounds the to and bottom surfaces of the diamond-shapedcross-section.
 16. The method of claim 15, further comprising: prior toforming the capping laver, forming an oxide layer that abuts the top andbottom surfaces of the source and drain regions.
 17. The method of claim16, wherein forming the protective layer comprises implanting carboninto the uppermost portion of the diamond-shaped cross-section.
 18. Themethod of claim 16, wherein the second etch removes the oxide layer andthe second portion of the capping layer from the bottom surfaces of thediamond-shaped cross-section while leaving the protective layer over theuppermost portion of the diamond-shaped cross-section.
 19. The method ofclaim 18, further comprising: after the second etch, forming a conformalconductive material on the top and bottom surfaces of the diamond shapedcross-section; and annealing the conformal conductive material to formthe source or drain contact.
 20. The method of claim 18, wherein thefirst etch and second etch have different etch chemistries from oneanother.
 21. A method, comprising: forming a fin that extends verticallyfrom a surface of a substrate and comprises source and drain regionswhich are separated from one another by a channel region, wherein thesource or drain region comprises epitaxial material with adiamond-shaped cross-section, and wherein a capping layer surrounds thediamond-shaped cross-section on its top and bottom surfaces; forming agate over an upper surface of the channel region and along sidewalls ofthe channel region; performing a first etch to remove a first portion ofthe capping layer surrounding the top surfaces of the diamond-shapedcross-section; and forming a protective layer configured to preventetching of the top surfaces in subsequent etch steps; and performing asecond etch to remove a second portion of the capping layer surroundingthe bottom surfaces of the diamond-shaped cross-section, while using theprotective layer to prevent etching of the top surfaces of thediamond-shaped cross-section by the second etch.